


Late Night

by Suliana



Series: Undertale Smuts [2]
Category: Undertale (Video Game)
Genre: Established Relationship, Fluffy Smut, Gift Fic, I can do fluffy smut, I want to say slow burn because its a great pun, I'm still so bad at tags, M/M, UTSS, but its not
Language: English
Status: Completed
Published: 2018-06-25
Updated: 2018-06-25
Packaged: 2019-05-28 03:45:48
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,039
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15039983
Author URL: https://archiveofourown.org/users/Suliana/pseuds/Suliana
Summary: Set well before the time of the game.Gaster is having a miserable day.  Good thing he has an attentive mate.





	Late Night

**Author's Note:**

  * For [SheeWolf85](https://archiveofourown.org/users/SheeWolf85/gifts).



> This is my UTSS gift to SheeWolf85 on Tumblr. She requested Grillby/Gaster and fluff...
> 
> Fluff is so hard to write lol. Is this fluffy? I don't even know. 
> 
> Meant to post this last night but SOMEBODY (me) fell asleep on top of their craptop. I'm so sorry - I swear I meant to.
> 
> I hope you enjoy it!

It had  _not_ been a good day.

Sure, it had started fine... in that he'd woken up.

His mate's side of the bed was cold, meaning it had been exceedingly late when he'd closed up the bar and chosen to spend the night there instead of traipsing home, probably through a snow storm.

His coffee pot had  _not_ automatically turned on like it was meant to.  Stars damn it.  He had a ph-fucking-D for the Angel's sake, and yet he couldn't the timer to work.

When he  _had_ managed to get coffee from the miserable device, he'd open the fridge to find no creamer, no milk, no  _nothing_.  Worse, someone must have used a damp spoon to scoop the sugar out of the bowl the previous day, so the sweetner was solidified into a solid lump.  Lovely.

Of course, then he had managed to dump half his mug down the front of his shirt, scalding his bones and making a downright mess on the floor.

His curses echoed throughout the empty house.

Gaster sighed, his skull cradled in his folded arms as he refrained from slamming it into his desk.  Work had been just a continuation of awfulness.  Data had been lost, power had been gone out... even his stars damned slide ruler had broken on him.

And he'd heard nothing from Grillby all day.

That wasn't a terrible surprise, the flame elemental was a busy monster.  But... he sighed again.  He was just frustrated beyond belief.  In the words of the Snowdin storekeepers... he was done.  He was just  _so_ done.

He stood, taking care to not trip on the legs of his chair.  That would just be the icing on the cake for the day, breaking his skull on his own desk.  

He pulled off his lab coat, ignoring the coffee stains down the front of it, and threw it onto the coatrack by the door.  He flicked the switch off, then glanced down the corridor.  "Sid?  I'm going home for the night, the CORE should be fine, but call me if anything comes up, ok?"

His current assistant, a gecko monster, peered around the corner, his tongue licking his eyeball as he grinned.  "About time you had an early night boss.  I'll make sure everything's fine, don't worry."  He licked his other eye, then vanished back around to where he was.

His eyelights shrank down to pin-pricks.  Sid was a good assistant, but he was  _young_.  But... he threw in the proverbial towel mentally.  He needed some time to himself, away from anything else that he could manage to break.  

Fuck it.  He was going home.

* * *

 Gaster shoved the door open, letting the snow drip off of him and onto the mat just inside the front door.  His shoes were absolutely destroyed, the leather soaked through, and shirt was clinging to his bones.

For a variety of monsters that didn't really feel temperature differences, he was  _cold_.

He grumbled, only noticing the delicious smell coming from the kitchen after he'd managed to get his shoes off and tossed to the side.  Savory and  _warm_.

He made a beeline for it, his briefcase being tossed carelessly to the couch.

Grillby glanced over his shoulder as his mate pushed into the kitchen, looking more like a fish monster than a skeleton.  His bones looked off and his clothing was stuck to his bones in what  _had_ to be an uncomfortable manner.  And the look...

He hummed, setting down the knife and the cucumber he had been preparing, and wiped his hands on his apron before pulling off his gloves.  His mate was just standing in the doorway, seemingly in a fog, and he took pity on the skeleton.

He really,  _really_ wanted to cuddle his mate against him, but he was far too wet.  Instead, he leaned forward and placed a peck on his cheek, keeping his flames in careful check.  "Go shower and dry off and I'll meet you upstairs?" he suggested, pressing a second kiss to his mate's teeth.

Gaster just nodded, turning and slumping his way up the stairs.  

Grillby sighed, letting his flames flicker back up in a reflection of his mood.  His mate pressed himself so very hard for monsterkind, but never stopped to take himself into consideration.  They'd talked about it, more than once, but the skeleton had protested about the CORE and the King and escaping back to the Surface... so much weight on one frail set of bones.

He fiddled about in the kitchen for a few long minutes, keeping an ear open.  As soon as the shower turned off, he put the food, now prepared and ready to serve, back in the refrigerator for later, and made his way up the stairs.

* * *

Gaster was already in their bed, curled up on himself, skull half-buried beneath the blankets and pillow.  He remained still as Grillby pushed the door half-shut behind him, leaving the room dark save for the sliver of light from the hallway and the ambient light from his own flames.  He remained still at the rustling coming from the doorway, the sounds of his mate's clothes hitting the floor, and continued to do so as the elemental slid under the blanket and spooned up against him.

Grillby pressed a single kiss to his mate's cervical vertebrae, tempering his flames as he wrapped an arm around the skeleton, pulling him closer.  His mate was still tense though, his spine rigid... that wouldn't do.

He traced his fingers up, making sure to keep his flames under strict control, and pressed his thumbs into his mate's shoulder blade, pushing a bit of warmth through his hands and into the bone.  He kept up the motion, easing to the other side of Gaster's spine, working on easing tension built up in the skeleton's mana lines.  

The rattling moan from his mate let him know that he'd found a blocked point, and he pressed a bit more heat into it, as well as a flick of green magic to ease the pain.  Slowly, so slowly, Gaster finally relaxed, his bones creaking as the tension suddenly drained from them.  

He shifted, facing his mate, and pressed a kiss of his own against Grillby's cheek, not even trying to bite back his purrs at the tickling of the flames against his mandible.  Grillby always knew how to calm him down after a bad day, he really didn't deserve his mate.

A flick between his eyes had him jerk back to awareness, realizing he'd spoken that aloud.  Grillby shook his head negative, a fleeting look of disappointment vanishing into his flames as he again pressed a kiss to his teeth, then pressed further, past, deepening the kiss.  

Gaster moaned again, letting his mate have his way as his magic began to swirl.  Being so close to his mate, being warm, with nothing pressing on him to steal his attention... it sent a shiver through him, one he didn't try to hide.  He let a tongue form around his mate's, magic pooling in his mouth as the elemental's hands traced down over his ribs, down his spine, pausing to stroke his floating ribs.

Stars, the heat and healing and  _intent_ his mate was pressing into him was amazing, calming and soothing, and more than enough to have him settle completely.  His sockets sank closed as his mate pumped his spine a few times as his fingers traced down lower, teasing the high arches of his pelvis,

Yes.  Yes, he needed this.

He didn't hold back a moan as Grillby's hand traced down his spine, palmed his pelvic girdle, then slowly, so very slowly, dragged a flaming finger through the coalescing magic it found.  He also couldn't help himself from his jerking as his magic snapped into existence, already damp and waiting.

Grillby gave him another kiss as his hands continued going down, his hands warming his mate's pelvis as he ran them over the high crests of his pelvis again.  Stars, his mate always knew how to calm him down and get him to settle after a bad day... his innate ties to his magic were similar to that of a skeleton monster's, meaning every touch, stroke, tickle - it held  _all_ of his intent towards him.

And it felt  _so_ good.

One hand continued stroking his pelvis as one trailed down even further, brushing the magic gathering between his femurs.  A sharp breath from behind him, brushing the back of his cervical vertebrae, followed a chuckle that sounded like the crackling of a campfire.  "Do you want to?" Grillby asked, and Gaster savoured every word.  His mate wasn't mute, but elementals were generally monsters of actions, not words, and getting more than a dozen words from him a day was impressive.

Gaster himself didn't hold back a groan as his magic was heated even more by the flames, each flicker sending little shivers through him.  "Please?" he asked, squirming over so he was on his back, Grillby pushing up so he was on his side, propped by an elbow, his one hand still at work low on his pelvis.

The elemental nodded, leaned in for a quick kiss, then shifted down the bed so he was settled between his mate's legs.  

The scientific part of Gaster's mind always tried to focus on the exact mechanics of an elemental's biology since they were so unlike all other monsters, but those thoughts were inevitably pushed from his mind as his mate  _pulled_ his tongue through his unformed magic, the intent of his mate's desire to bring him  _pleasure_ overriding everything else.  Another stroke of the tongue and his magic formed a pussy shamefully fast, like he was a youngling just out of stripes experimenting for the first time.

Another chuckle, and that tongue pressed against his newly formed channel, pressing  _in_ , and a clever thumb wreathed in tickling flames found its way to his clit, rubbing broad circles around it.  

The keen that pulled from his throat also made him feel like a randy teenager again, but only for a moment as Grillby licked a stripe over it, driving thoughts concerning logic and science away.  There were fingers in him, stretching him, and he bucked against them, his sockets closing as he let himself _feel_.  

And then there was a _mouth_ on his clit, giving it a hard suck, a brush of teeth, and he trembled as the fingers brushed something  _delightful_.  "Griiiiiiiiiillbyyyyyyyy-"

The hand pulled away, the beautifully  _hot_ mouth left him, and his ecto felt strangely cold as his mate, his lover repositioned himself.  He cracked a socket, throwing an arm up and catching the elemental around his shoulders and pulled him in for a kiss, sweet and slow.  He pulled back, just far enough to whisper "Please?" before resuming the contact, his other hand coming to rest on Grillby's hip.  

His mate really was too good to him.  Another chuckle, and the heavy weight of a cock brushed his femur, then stroked up and down the slit formed in his ecto.  It  _burned_ , tickled,  _throbbed_ as it pushed in, the pace slow and steady until a pair of hips sheathed in flame met bone, coming to a rest.  Both panted, foreheads coming to rest together for a moment as they adjusted.  

And then Grillby started to  _move_ , and Gaster's bones creaked as he strained to open himself further, to give more of himself to his lover.  Time was meaningless as flames caressed, held him,  _warmed_ him, and Grillby moaned wordlessly against the side of his head as he continued.

It didn't take long for Gaster to arch, his spine lifting off the mattress and arching like a bow, rising up to meet the last stuttering thrusts from Grillby, and they both slumped as they slowly came down from their highs.  

He felt boneless (heh) but he flopped himself over, pulling Grillby so his head was resting on his clavicle, stroking his phalanges slowly though the still-dancing tendrils of fire.  A kiss to his forehead and he let his sockets sink closed, deciding to deal with the cleanup at some undefined point in the future.   _Later_.  That would suffice.

It had already been a long enough day.

**Author's Note:**

> Again, I hope you liked it. <3


End file.
